Etching apparatus



April 7, 1936. E, F. KINZLER ETCHING APP ARATUS Filed Aug. 5, 1935INVENTOR Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE Claims.

My invention relates more particularly to the etching of plates such asare employed in the photoengraving and analogous arts, and moreparticularly to the subjecting of said plates to 5 the action of acidsolutions which are employed for producing relief on the printingsurface of the plate, but it will be understood that various features ofthe invention are capable of use in other ways.

One object of my invention is to provide apparatus of the characterreferred to wherein there is more uniform distribution of liquid spreadover the surface of a plate and consequently more uniform etchingthereof than in various forms of apparatus heretofore employed.

Another object of my invention is to provide an improved manner ofcirculating the acid solution and controlling the rate of supply thereofto the plates being treated to control the etching rate on the plates.

Still another object of my invention is to provide apparatus whereby thehandling of the plates is facilitated, together with means forautomatically subjecting the plates to a washing operation, uponwithdrawal thereof from the acid-treating cabinet.

A further object of my invention is to provide an apparatus of thecharacter referred to of generally simplified and improved form, wherebyturning and acid-brushing of the plates is eliminated.

As shown in the accompanying drawing, Figure 1 is a side elevationalview of the apparatus; Fig. 2 is a vertical sectional view thereof,looking from the left-hand end of Fig. 1; Fig. 3 is an enlargedsectional view of a portion of the apparatus of Fig. 1, and Fig. 4 is aview taken on the line IVIV of Fig. 1, on an enlarged scale.

The apparatus includes a treating or acid chamher 5 which is mountedupon a suitable table or supporting frame 8, and which may suitably beformed of acid-resisting metal or enameled steel plates. A washing tankI is also mounted upon the framework 6.

The chamber 5 normally contains a body of acid solution or mordant ofsubstantial volume and depth, as indicated at 8, and said solution iscirculated by means of a pump 9 which is driven from a motor Hi. Thesolution is drawn from the tank through a pipe H, and forced by the pump9 upwardly through a pipe l2, which discharges into a spray head l3. Thespray head extends across and closes the major portion of the rmostportion of the chamber 5, and a perforated wall or plate l4 extendsacross the lower side of the spray head and is provided with a largenumber of perforations distributed throughout its area.-

The acid solution is preferably supplied to the spray head rapidlyenough to maintain substantial pressure within the spray head, so thatthe solution will be sent through the perforations of the plate M withconsiderable force.

A perforated baflie plate i5 is provided in the path of flow from thepipe l2, and this plate is provided with perforations which arepreferably somewhat larger than perforations in the plates it, so thatwhile the plate l5 will assist in effecting distribution of the liquidsomewhat uniformly through the spray head, nevertheless the sprayopenings or perforations directly beneath the plate 15 will receive anadequate supply of liquid. A control valve It serves to regulate flowthrough the pipe l2, and has a stem or handle that is located inproximity to a graduated scale ii that is positioned on the side of thechamber 5. The motor ill is usually driven at a constant speed, so thatwhen the valve i6 is positioned at a certain point with respect to thescale ii, a given number of gallons of solution per minute will besupplied to the spray head. I have found that good results are securedby supplying liquid at from 50 gallons to gallons per minute, the

rate per minute, of course, depending upon the relative coarseness orfineness of the Work.

Slide rails or track rails l9 extend across the wash tank I and into thechamber 5. A tray or plate rest 20 is slidably supported upon the railsl9, and has its bottom preferably of lattice or mesh-like form, so thatthe acid spray can pass through those portions thereof which are notcovered by a photo engraving print or plates. Plates 2| which are to besubjected to the acid solution are placed upon the tray 20 which is thenslid past a swinging door or gate 22, into the chamber 5, where theplates will be disposed directly beneath the spray head and be subjectedto the action of the downwardly discharged solution.

The tray is preferably of such size as to receive four plates comprisinga set of plates employed in color printing. The area of the perforatedplate It is preferably equal to the area of the tray 20, so that aplurality of plates to be treated will be uniformly subjected to theaction of the solution.

Circulation of air through the chamber 5, and removal of gases from thechamber is secured by means of hooded air inlets 24 at the sides of thechamber, through which atmospheric air may enter during exhaust ofvapors and gases from the upper end of the chamber. Forced draft orexhaust from the chamber 5 is secured by a pump or blower 25 which drawsthe air and gases from the tank and discharges the same through a pipe26 to a point vwhere such fumes and gases will not affect the operator.

When the plate or plates contained on the tray 20 have been subjected tothe acid solution for a sufficient period of time, the tray is withdrawnthrough the door 22. A grid or bar 20" projecting upwardly from the tray20, pushes the door 22 in either direction, when the tray is insertedinto and withdrawn from the chamber I. Upon the withdrawal movement ofthe tray, the bar pushes the door 22 against a lever 28 which opens avalve 29 so that flushing water may flow from a water supply pipe an toa water spray pipe 3|, and be discharged upon the etched plate to washthe acid therefrom.

The wash water will flow into the tank I, from which it may be drawn offthrough a waste pipe 32 to which a drain pipe 33 from the chamber I isalso connected, for the withdrawal of waste acid and flushing water fromthe chamber when it is desired to change the acid solution.

The plates may then be subjected to drying air that may be supplied froma blower 34.

through a pipe 35 which will lead to a suitable position above theplate. The blower 34 may conveniently be driven by a motor 36 which alsodrives the draft fan or blower 25.

I'he acid solution in the chamber 5 may conveniently be replenished bythe introduction of acid to a charging chamber 38, and by admittingwater to said chamber through a tap 39 that has connection with thewater supply pipe 30.

In the etching operation, it is, of course, necessary that the shadows,half-tones and highlights be fully and accurately developed on theplates, and it is particularly important that the etching for thevarious tones be uniform over the entire surface of each plate. There ispresent on the surface of the plates 2. scum which, heretofore, theoperator has attempted to remove before inserting the plates into theacid chamber by brushing, but this brushing has not been satisfactory oreffective to remove the scum entirely. I have found, however, that suchbrushing is unnecessary, since the scum is effectively removed by theaction of the downwardly discharged solution, particularly when theliquid is supplied at a high rate per minute, for example, at a ratebetween 85 and 90 gallons per minute for a short period of time.

After the scum has been removed, the rate of flow is lowered and theplates subjected to the acid spray for a sufficient period of time todevelop fully the shadows. During this period, it is unnecessary, asformerly practised, to remove the plates and turn them relative to theirformer position, usually four times, in order to render the etchinguniform over the plates.

Apparently, uniformity of etching and the elimination of such plateturning is due to the proper distribution of the acid by the ballleplate l5 through the spray head, and its discharge therefrom underpressure and at a suflicient rate of flow that the plates are subjectedto fresh acid which is eifective to wash away the contaminated acid.

After the shadows or details are etched properly in the plates, thevalve is actuated to increase the rate of flow, to develop the middletones, and further actuated to increase the rate of flow to possibly 90gallons per minute to bring out the highlights. However, the period oftime that the plates are exposed or subjected to the high volume flow ismuch less than the period of time that the plates are subjected to thelow volume flow, but, in practice, the entire time required for properetching of fine work is approximately fifty percent lower than the timerequired by methods heretofore practised.

Not only are the plates uniformly etched over their entire surface, butthe production of a set of plates utilized in color printing havingexactness in characteristics is facilitated by the uniformity of etchingunder the downwardly discharged acid solution, so that the plates ineffect are duplicates.

when etching coarser work, a high volume acid discharge is employed todecrease the time required for etching the plates.

I claim as my invention:--

1. Etching apparatus comprising a treating chamber adapted to contain abody of liquid in its lower portion. means for supporting a plate abovesaid liquid, a downwardly-discharging spray head at the upper end ofsaid chamber and extending across the-major portion of the chamber, apipe communicating with said spray head, a pump device for withdrawingliquid from a lower portion of the chamber, and discharging it throughsaid pipe into the spray head, and a perforated baiiie plate disposed inthe path of flow of said liquid as it enters the spray head.

2. Etching apparatus comprising a treating chamber adapted to contain abody of liquid in its lower portion, means for supporting a plate abovesaid liquid, a downwardly-discharging spray head at the upper end ofsaid chamber and extending across the major portion of the chamber, apipe for conveying liquid into said spray head, and a perforated baiileplate disposed in the path of the liquid which enters the spray head.

3. Etching app atus comprising a treating chamber adapted to contain abody of liquid in its lower portion, means for supporting a plate abovesaid liquid, a downwardly-discharging spray head at the upper end ofsaid chamber and extending across the major portion of the chamber, apipe for conveying liquid into said spray head, and a perforated baiileplate disposed in the path of the liquid which enters the spray head,the baiile plate being of small area relative to the area of the sprayhead, and provided with perforations of substantially larger area thanthe perforations in the spray head.

4. Etching apparatus comprising a treating chamber wherein photographicplates may be subjected to the action of a liquid, a tray for supportingphotographic plates and movable into the said chamber, a swinging doorin one wall of the said chamber, and means on the tray for pushing saiddoor from its closed position to an open position, during movement ofthe tray into and out of said chamber.

5. Etching apparatus comprising a treating chamber wherein photographicplates may be subjected to the action of a liquid, a tray for supportingphotographic plates and movable into the said chamber, a swinging doorin one wall of the said chamber, means on the tray for pushing said doorfrom its closed position to an open position, during movement of thetray into and out of said chamber, the door being swingable inwardly andoutwardly, and a flushing valve device positioned to be operated by thedoor upon outward swinging movement thereof during withdrawal movementof the tray.

EpwARn F. KINZLER.

